The advance publicity is seductive. From the top of Mt. Diablo in San Francisco's East Bay, one can see apparently more of the Earth's surface than from any point on the planet with the exception of Japan's Mt. Fuji. Out past Yosemite's Half Dome to the snow-capped Sierras in the east, past the Farallon Islands in the Pacific to west, to the south the land falls away revealing the Santa Cruz Mountains and to the north, incredibly, one can see Mount Lassen in the Cascades. The 30,000 square mile panorama is more expansive than even that from Everest.
That's the advance publicity.
In reality, if you stand atop Mt. Diablo you can see about 10 feet in each direction, the view being blocked by the walls of the gift shop and museum built right there on the summit. The peak actually comes up through the gift shop floor, a rocky out-cropping breaching the polished concrete giving the absurd impression that the shop preceded the moment of creation, and only later did the mountain thrust upwards through the floor. Standing on the summit, one can admire not the advertised postcard view, but a view of the postcards -- and novelty pens, key rings, snacks and brochures celebrating the great natural reserve that is Mount Diablo State Park.
Whoever thought the experience of a four-hour hike to the summit would be enhanced by the opportunity to buy a cheap t-shirt was mistaken.
To take in the real view, one must exit the gift shop and climb the stairs to the roof. The view is spectacular, and as one is 10 feet above the summit, theoretically even better. But you are standing on a gift shop roof.